Upstairs, downstairs
Japan Airlines used to have 747s with economy seats in the upper deck also. Figuring it was likely to be my only opportunity to travel up there I naturally selected an upper deck seat for a hop I did from Seoul to Tokyo in 2010.
I did actually fly in the business class nose section with KLM to Tokyo a couple of years ago but that was still only on an economy ticket (and with economy meals) - they must have only needed the upper deck for business class so decided to sell a few more economy tickets and opened up that section in the seat selection map on the web site. Got in there for the return leg as well!